We
have previously found a positive association between milk consumption
and prostate cancer risk using meta-analysis to analyze published
case-control studies. In the present study, further meta-analysis was
conducted to estimate the summary relative risk (RR) between the
consumption of milk and dairy products and prostate cancer from cohort
studies published between 1966- 2006. We found 18 relevant articles and
13 independent studies were available for our analysis. The summary RR
was 1.13 (95% confidence interval = 1.02-1.24) when comparing the
highest with the lowest quantile of consumption. The summary RRs by
study stratification showed a positive association. A dose-response
relationship was identified when combining the studies that partitioned
the consumption by quintiles. We also evaluated the effects of some
limitations, such as dairy classification, prostate cancer stages and
publication bias, in the present study. These findings, together with
the previous study, suggest that the consumption of milk and dairy
products increases the risk of prostate cancer. This is biologically
plausible since milk contains considerable amounts of fat, hormones,
and calcium that are associated with prostate cancer risk.